In procedural programming languages such as LISP, Ruby and Python, the definition information about variables and functions is read at the time of execution of a program, and the program is executed based on the read function definitions and variable values. The software for interpreting and executing such a procedural programming language reads an application program that is described in the procedural programming language, at every time of startup, and thereafter, processes input data and outputs a processing result in accordance with the read application program.
As a feature of the software for interpreting and executing a procedural programming language, once a defined variable name is input, the content of the variable can be read out, and once a function for reading a defined function is input, the function code can be output.